The invention relates to railroad car trucks or bogies which are generally fabricated from a number of rigid metal parts, and especially to the bolsters which are connected between the sideframes of the trucks. More particularly, the invention relates to bolsters which are used in rigid H-type frames and Ladder-type frames which are employed in dual axle and triaxle trucks of heavy freight cars. It is important that the bolster and its end connections with the sideframes of such trucks be rigid to resist bending of the bolster under high vertical and longitudinal loads imparted to the bolster through the sideframes and resisted at the center of the bolster, as the truck moves along a railroad track. Incongruent as it may seem, the bolster ends connected to the sideframes should also be relatively flexible to accommodate twisting loads which are imparted to the bolster through the sideframes as the truck moves, for example, over wavy or uneven sections of railroad track. The invention is directed to the provision of a bolster which meets both of the requirements indicated above.
Briefly stated, the invention is in a bolster which has a generally hollow, box-like frame or construction which terminates short of the opposing bolster ends which are connected to the adjacent sideframes. This particular bolster construction is extremely rigid and able to resist the aforementioned bending stresses or loads which are highest at the center of the bolster. The box-like construction at each end of the bolster is transformed into a more flexible I-shaped section which is secured to an adjacent sideframe of the truck. The I-shaped section provides the necessary flexibility and rigidity to meet both of the loading conditions mentioned above.